HARRISBURG — People signing up for new phone numbers in the 724 area code, which includes Butler County, soon may end up getting a new area code. The state Public Utility Commission announced today that it would be activating the 878 area code in areas covered by the 724 and 412 area code. The commission recently discovered that the 724 area code nearly is exhausted, so the activation of the new area code will begin in that area code. The commission implemented the 878 area code in 2000 for when the 412 and 724 area codes ran out, but has not had to use the new number until now. Current customers will keep the same area code and phone number, but existing customers adding a new phone line or new customers would be assigned the 878 area code. Activation of the new area code in the 412 area code, which includes most of Allegheny County and small portions of Washington and Westmoreland counties, will not happen until all numbers in the 412 area code have been exhausted. The 724 area code covers all of Beaver, Butler, Greene and Lawrence counties and parts of Allegheny, Armstrong, Clarion, Crawford, Fayette, Indiana, Mercer, Venango, Washington and Westmoreland counties.